Document generated on 09/29/2021 2:56 p.m. Géographie physique et Quaternaire A Reconnaissance Geophysical Survey of the Kawartha Lakes and Lake Simcoe, Ontario Levé géophysique de reconnaissance des lacs Kawartha et du lac Simcoe, Ontario Eine geophysikalische Erkundung und Vermessung der Kawarthaseen und des Simcoesees, Ontario Brian J. Todd and C. F. Michael Lewis La néotectonique de la région des Grands Lacs Article abstract Neotectonics of the Great Lakes area A marine geophysical survey program has been conducted in lakes of southern Volume 47, Number 3, 1993 Ontario. The survey was designed to detect neotectonic features, if they exist, and to evaluate their geological importance. High-resolution single- and URI: https://id.erudit.org/iderudit/032960ar multichannel seismic reflection profiling were used to delineate late- and DOI: https://doi.org/10.7202/032960ar post-glacial sedimentary strata and structures, as well as the sediment/bedrock interface, in the Kawartha Lakes and Lake Simcoe. Results show that two seismostratigraphic sequences are common within the unconsolidated See table of contents overburden. The lower unit exhibits a parallel reflection configuration having strong reflection amplitudes, whereas the upper unit is acoustically transparent and overlies the lower unit conformably in some places and Publisher(s) unconformably in others. Both units vary in thickness within lakes and from lake to lake. Typical subbottom profiles of Precambrian rock surfaces are Les Presses de l'Université de Montréal rolling; those of Paleozoic rock surfaces are smooth. At one location in Lower Buckhorn Lake, tilted rock surfaces may be faulted but disturbance of ISSN overlying glacioge-nic sediments was not observed. In western Lake Simcoe 0705-7199 (print) and Kempenfelt Bay, slumping into graben-like features was observed. Also in 1492-143X (digital) Lake Simcoe, a diapiric feature was documented. It is speculated that these disturbances most likely result from glacier ice block melting and fluid migration. A tectonic origin, however, cannot be discounted at this stage of Explore this journal investigation. Additional systematic marine geophysical surveys are required in the future to map features in detail to determine whether they are of neotectonic or glaciotectonic origin. Cite this article Todd, B. J. & Lewis, C. F. M. (1993). A Reconnaissance Geophysical Survey of the Kawartha Lakes and Lake Simcoe, Ontario. Géographie physique et Quaternaire, 47(3), 313–323. https://doi.org/10.7202/032960ar Tous droits réservés © Les Presses de l'Université de Montréal, 1993 This document is protected by copyright law. Use of the services of Érudit (including reproduction) is subject to its terms and conditions, which can be viewed online. https://apropos.erudit.org/en/users/policy-on-use/ This article is disseminated and preserved by Érudit. Érudit is a non-profit inter-university consortium of the Université de Montréal, Université Laval, and the Université du Québec à Montréal. Its mission is to promote and disseminate research. https://www.erudit.org/en/ Géographie physique et Quaternaire, 1993, vol. 47, n° 3, p. 313-323, 9 fig. A RECONNAISSANCE GEOPHYSICAL SURVEY OF THE KAWARTHA LAKES AND LAKE SIMCOE, ONTARIO* Brian J. TODD and CF. Michael LEWIS, Terrain Sciences Division, Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A OE8, and Atlantic Geoscience Centre, Geological Survey of Canada, Bedford Institute of Oceanography, P.O. Box 1006, Dartmouth, Nova Scotia B2Y 4A2. ABSTRACT A marine geophysical survey RÉSUMÉ Levé géophysique de reconnais­ ZUSAMMENFASSUNG Eine geophysika- program has been conducted in lakes of sance des lacs Kawartha et du lac Simcoe, lische Erkundung und Vermessung der southern Ontario. The survey was designed Ontario. Le levé a été mené afin de déceler Kawarthaseen und des Simcoesees, to detect neotectonic features, if they exist, les éléments néotectoniques et d'évaluer Ontario. Ein marines geophysikalisches and to evaluate their geological importance. leur importance géologique. Des profils de Vermessungsprogramm wurde in Seen von High-resolution single- and multichannel sismique réflexion de haute résolution ont Sùdontario durchgefuhrt. Die Vermessung seismic reflection profiling were used to servi à déterminer les couches et les struc­ war angelegt, um eventuell vorhandene neo- delineate late- and post-glacial sedimentary tures sédimentaires tardi- et postglaciaires tektonische Elemente zu entdecken und ihre strata and structures, as well as the ainsi que l'interface sédiment- roche en place geologische Bedeutung zu bestimmen. sediment/bedrock interface, in the Kawartha dans les lacs Kawartha et le lac Simcoe. Les Seismische Reflexionsprofile einfacher oder Lakes and Lake Simcoe. Results show that résultats montrent qu'il y a deux séquences mehrfacher Frequenz mit hoher Auflôsung two seismostratigraphic sequences are com­ sismostratigraphiques communes dans la wurden benutzt, um die spàt- und postglazia- mon within the unconsolidated overburden. couverture de dépôts meubles. L'unité infé­ len Sedimentschichten und -strukturen The lower unit exhibits a parallel reflection rieure présente une configuration de sowie das Interface Sediment/anstehendes configuration having strong reflection ampli­ réflexion parallèle avec de fortes amplitudes, Gestein in den Kawarthaseen und dem tudes, whereas the upper unit is acoustically alors que l'unité supérieure est transparente Simcoesee zu bestimmen. Die Ergebnisse transparent and overlies the lower unit con­ du point de vue acoustique et recouvre zeigen, dafî es zwei gemeinsame seismos- formably in some places and unconformably l'unité inférieure parfois en concordance, tratigraphische Sequenzen innerhalb der in others. Both units vary in thickness within parfois en discordance. L'épaisseur des nicht verfestigten Uberlastung gibt. Die lakes and from lake to lake. Typical subbot- deux unités varie à l'intérieur d'un lac et d'un untere Einheit zeigt eine Paralell- tom profiles of Precambrian rock surfaces lac à l'autre. Les profils caractéristiques des Reflektorstruktur mit starken Reflexion- are rolling; those of Paleozoic rock surfaces surfaces précambriennes sont ondulés, tan­ sweiten, wohingegen die hôhere Einheit are smooth. At one location in Lower dis que ceux des surfaces paléozoïques sont akustisch transparent ist und die untere Buckhorn Lake, tilted rock surfaces may be plats. En un site du Lower Buckhorn Lake, Ia Einheit an einigen Stellen gleichgelagert und faulted but disturbance of overlying glacioge- surface de roches basculées est peut être an anderen ungleich gelagert bedeckt. Die nic sediments was not observed. In western faillée, mais on n'a observé aucune pertur­ Dicke der beiden Einheiten variiert innerhalb Lake Simcoe and Kempenfelt Bay, slumping bation dans les sédiments glaciaires sus- der Seen und von einem See zum anderen. into graben-like features was observed. Also jacents. Dans la partie ouest du lac Simcoe Die typischen Unterbauprofile der pràkam- in Lake Simcoe, a diapiric feature was docu­ et la Kempenfelt Bay, on a observé des glis­ brischen Felsoberflachen sind wellig, die der mented. It is speculated that these disturb­ sements dans des formes ressemblant à des palàozoischen Felsoberflachen glatt. An ances most likely result from glacier ice block grabens. On a également relevé une forme einer Stelle im unteren Buckhornsee sind die melting and fluid migration. A tectonic origin, diapirique dans le lac Simcoe. On croit que gekippten Felsoberflachen vielleicht verwor- however, cannot be discounted at this stage ces perturbations sont probablement le fen, doch beobachtet man keine Stôrung der of investigation. Additional systematic résultat de la fonte de blocs glaciaires et de darùbergelagerten glaziogenen Sedimente. marine geophysical surveys are required in la migration de fluides. À ce stade des Im westlichen Simcoesee und der Kem­ the future to map features in detail to deter­ recherches, on ne peut toutefois pas écarter penfelt Bay hat man Abrutschungen in gra- mine whether they are of neotectonic or gla- une origine tectonique. On devra effectuer benartige Formen festgestellt. AuBerdem ist ciotectonic origin. un levé géophysique systématique afin de im Simcoesee eine diapire Form dokumen- cartographier toutes les formes et de déter­ tiert. Man vermutet, dafî dièse Stôrungen miner leur origine néotectonique ou hôchstwahrscheinlich auf das Schmelzen glaciotectonique. von Gletschereisblôcken und flùssige Wanderungen zurùckzufùhren sind. In- dessen kann in diesem Stadium der Forschung ein tektonischer Ursprung nicht ausgeschlossen werden. * Geological Survey of Canada Contribution no. 47592 Manuscrit révisé accepté le 3 août 1993 314 BJ. TODD and C.F.M. LEWIS INTRODUCTION highly developed transportation corridor, industrial base and power generation and distribution system. A regional marine Over the last decade, there has been increased concern seismic survey has been undertaken in western Lake Ontario about the identification and documentation of neotectonic (Lewis et al., 1992). The objective of this paper is to report activity and related geological features in southern Ontario, results from a reconnaissance marine seismic investigation one of the most populated areas of Canada (Wallach and of the sediments and bedrock beneath the Kawartha Lakes Mohajer, 1990; Mohajeref a/., 1992). Although both subaerial and Lake Simcoe in the region north of metropolitan Toronto. and subaqueous geological evidence of